1. Field of the Invention
The present invention relates to a method and apparatus for reproducing information, which read compressed audio data from an information recording medium in which the compressed audio data is recorded in a frame unit and subjects the compressed audio data thus read to an expansion processing to reproduce same, and more particularly to such a method and apparatus having a function of a fast forwarding reproduction in which frame regions to be reproduced and the other frame regions not to be reproduced are repeated alternately.
2. Description of the Related Art
There has recently been popularized a compression system in which a musical audio data is subjected to a compression processing to generate a compressed audio data and the compressed audio data is subjected to an expansion processing to reconstitute the original audio data. As such a compression system, the MP3 (MPEG Audio Layer-3) format is known for example. The MP3 format is excellent in that a data size can remarkably be reduced in comparison with the original audio data.
An information reproducing apparatus to which the above-described compression system is applied, has a function of reading out the compressed audio data, which has been recorded in an information recording medium such as a CD or a flash memory. In general, the compressed audio data has a data structure with divided frames so that each of the frames includes a header information and a main body as the compressed audio data. When a normal reproduction is carried out with the use of the information reproducing apparatus, the frames are read out successively to make reproduction in a reading-out order. It is preferable that the information reproducing apparatus can perform not only the normal reproduction, but also a special reproduction. A fast forwarding reproduction is a typical example of the special reproduction. A user can conduct the fast forwarding reproduction is carried out when listening to music, thus making it possible to recognize the position of music being reproduced so as to provide useful effects. In order to achieve such a fast forwarding reproduction, there is required control of repeating a skipping operation of a plurality of frames after reproduction of the frames in the information reproducing apparatus.
With respect to the above-mentioned compression system, there exist a constant bit rate system in which the same bit rate is set for the respective frames and a variable bit rate system in which different bit rates are set for the respective frames. When the above-mentioned fast forwarding reproduction is performed, the constant bit rate system in which relationship between time and a data size becomes linear so that the frame size of each of the frames becomes constant, makes it possible to determine previously a position of the subsequent frame to make easily control of skipping a plurality of frames. On the other hand, the variable bit rate system in which the frame size varies, requires measures to determine the position of the subsequent frame with the use of a suitable method. With respect to an ordinary method, it is conceivable that a positional information such as an address for the respective frames is previously obtained and the thus obtained information is stored as a map in a memory so that the above-mentioned fast forwarding reproduction is carried out with reference to the map.
Previous preparation of the map for the entirety of the information recording medium in which the compressed audio data has been recorded, requires much time. It is also necessary to ensure the memory having a sufficient storing capacity in order to preserve the map. Accordingly, increase in processing load and a required capacity of a memory becomes a problem, in order to perform the fast forwarding reproduction based on the compression system of the variable bit rate system.
An object of the present invention, which was made to solve the above-described problems, is therefore to provide a method and apparatus for reproducing information, which permits to relieve increase in processing load and a required capacity of a memory so that the compressed audio data is read out from the information recording medium to make a special reproduction such as a fast forwarding reproduction.
In order to attain the aforementioned object, the method of the present invention for reproducing information, comprises the steps of:
reading compressed audio data from an information recording medium in which the compressed audio data is recorded in a frame unit; and
subjecting the compressed audio data thus read to an expansion processing to reproduce same,
wherein:
when an instruction is given to make a special reproduction in which a frame region to be reproduced and an other frame region not to be reproduced are mixed, control is made so that the compressed audio data in respective frames are successively reproduced in the frame region to be reproduced, and a header information for the respective frames is read out in the other frame region not to be reproduced, and determination on a leading position of a subsequent frame is made on a basis of the header information, thereby conducting a successive migration for the respective frames.
The apparatus of the present invention for reproducing information, which reads compressed audio data from an information recording medium in which the compressed audio data is recorded in a frame unit and subjects the compressed audio data thus read to an expansion processing to reproduce same, the apparatus comprises:
an instruction device for giving instruction to make a special reproduction in which a frame region to be reproduced and an other frame region not to be reproduced are mixed; and
a reproduction control device for making control so that the compressed audio data in respective frames are successively reproduced in the frame region to be reproduced, and a header information for the respective frames is read out in the other frame region not to be reproduced, and determination on a leading position of a subsequent frame is made on a basis of the header information, thereby conducting a successive migration for the respective frames, when the special reproduction is instructed.
According to the above-mentioned method and apparatus of the present invention, when the special reproduction such as the fast forwarding reproduction is instructed during reproduction of the compressed audio data, control is made so that the frame region to be reproduced normally and the other frame region to be skipped without being reproduced are repeated. In this case, control is made to repeat the steps of reading out a header information for the respective frames to analyze same and determining a leading position of the subsequent frame, when conducting a successive migration for the respective frames in the frame region not to be reproduced. In case where the skipping operation of the frame is required upon making a special reproduction in a state that the arrangement of the frames cannot be determined previously, it is possible to determine surely the leading position of the respective frame without previously preparing the map, thus reducing the processing load and the capacity of the memory.
In the above-mentioned method and apparatus of the present invention, the special reproduction may comprise a fast forwarding reproduction in which the frame regions to be reproduced that comprise continuous frames having a number of xe2x80x9cSxe2x80x9d and the other frame regions not to be reproduced that comprise continuous frames having a number of xe2x80x9cMxe2x80x9d are repeated alternately. According to such a feature of the present invention, control is made for the compressed audio data with divided frames so that the frames having the number of xe2x80x9cSxe2x80x9d are continuously reproduced in the frame region to be reproduced, on the one hand, and the frames having the number of xe2x80x9cMxe2x80x9d are continuously skipped in the frame region not to be reproduced. Accordingly, it is possible to carry out the fast forwarding operation in which reproduction and a search alternate after a certain interval of time. In addition to such an effect, a user can easily recognize the position of the music being reproduced.
In the above-mentioned method and apparatus of the present invention, the compressed audio data may be generated based on a variable bit rate system in which different bit rates are set for the respective frames. According to such a feature, the variable bit rate system, which is applied as the compression system to generate the compressed audio data, makes it possible to determine the leading position of the frame to conduct an easy skipping operation without previously preparing any map, while the respective frames have the different frame size from each other.